The overall objective of this project is to assist in developing more effective and more generally acceptable methods for prevention and treatment of human pulmonary tuberculosis than are available currently. This objective is being approached primarily in the well documented rhesus monkey model via: (1) assessments of the therapeutic accomplishments of isoniazid and rifampin, administered singly and in combination; (2) determination of the minimal duration of treatment with a combination of the above agents required for maximal benefits; and (3) evaluation of the pathogenicity of rifampin-resistant tubercle bacilli for guinea pigs and monkeys.